This application is a 371 of PCT/EP 98/05585 filed Sep. 3, 1998.
The invention relates to a process for preparing structured organic-inorganic hybrid materials using amphiphilic block copolymers as templates. The process of the invention can also be used to prepare macroscopically anisotropic formed pieces, mesoporous solids and inorganic formed pieces in the nanometer range. The invention also comprises the materials prepared and their use, in particular in separation technology and in heterogeneous catalysis, and in the microelectronics industry.
Organic-inorganic hybrid materials with structures in the nanometer range are a class of materials with varied and interesting properties. Materials of this type are used in catalysis, membrane technology and separation technology, and also in developing nanoscopic structures. In particular materials in which the structures have a large length range are likely to have varied applications.
Conventional processes for preparing structured materials use self-assembling surfactants as structuring templates. The morphology of the inorganic materials is determined here by the way the surfactant molecules organize. Processes of this type have been used in particular to prepare inorganic mesoporous materials, and the surfactants used here have had low molecular weight (N. K. Raman et al., Chem. Mater. 8 (1996), 1682; U.S. Pat. Nos. 5,057,296; 5,108,725; 5,098,684 and 5,102,643). However, the aim of these processes has been to form mesoporous inorganic solids rather than an organic-inorganic hybrid material. In addition, control of structure during the conduct of the process is extremely difficult due to phase changes. Using surfactants as templates, furthermore, it is only possible to obtain mesoporous solids with relatively small pores in the range from 2 to 10 nanometers. Already at pore sizes above about 5 nanometers the inorganic solids described begin to become mechanically unstable and collapse, due to insufficient wall thicknesses. A further disadvantage is that the mesoporous solids obtained by this process can be obtained only as fine powders.
The use of lyotropic liquid-crystalline phases of low-molecular-weight surfactants has recently been described for preparing mesoporous solids (Attard et al., Nature 378 (1995), 366-367). Strict separation between aqueous (polar) and hydrophobic (nonpolar) regions in lyotropic liquid-crystal phases of this type permits the formation of an ordered structure. Polycondensation of an inorganic water-soluble monomer consolidates the inorganic material and produces a copy of the liquid-crystal structure. This makes it possible to form not only fine-grained powders but also nanostructured mesoporous monoliths. Moreover, these processes, too, serve to prepare a mesoporous material rather than an organic-inorganic hybrid material. The low-molecular-weight surfactants used moreover give only relatively low pore diameters.
The use of a lyotropic liquid-crystal phase made from amphiphilic block copolymers as a template has also been proposed for preparing mesoporous inorganic materials (C. G. Gxc3x6ltner et al., Adv. Mater. 9(5) (1997), 431-436). Stable mesoporous materials with pore sizes of from 7 to 15 nanometers could be obtained in this way. However, no further details concerning suitable amphiphilic block copolymers have been disclosed.
It was therefore an object of the invention to provide a process for preparing structured organic-inorganic hybrid materials while overcoming at least some of the disadvantages of the prior art.
The invention achieves this object by means of a process for preparing structured organic-inorganic hybrid materials, comprising the steps:
(a) forming a mixture comprising at least one mesophase of an amphiphilic organic block copolymer having at least one hydrophilic block and at least one hydrophobic block as template and comprising at least one precursor which can be reacted to give an inorganic solid,
(b) reacting the precursor,
(c) optionally removing any volatile constituents from the reaction mixture, and
(d) obtaining the organic-inorganic hybrid material,
wherein a hydrophobic block of the amphiphilic block copolymer has a glass transition temperature Tgxe2x89xa650xc2x0 C.
According to the invention a mixture is first formed which comprises at least one mesophase of an amphiphilic block copolymer as template and comprises at least one precursor which can be reacted to give an inorganic solid. An amphiphilic block copolymer is composed of at least two blocks of different polarity, of which one is hydrophobic and the other hydrophilic, in particular water-soluble. Reacting the precursor gives an inorganic solid, either surrounding the amphiphilic block copolymers present as template of being embedded into these. During the reaction of the precursor to give the solid any volatile constituents which may have been produced are removed from the reaction mixture so that they cannot interfere with the mesophase.
Surprisingly, it has been found that use of an amphiphilic block copolymer with a glass transition temperature Tgxe2x89xa650xc2x0 C. allows for controlled establishing of various structures by varying the amount of precursor added. Using a polymer of this type allows an equilibrium morphology to be obtained, and suitable selection of the amounts of the starting compounds can therefore predetermine the structures. Increasing the proportion by volume of the inorganic precursor in relation to the polymer gives the morphologies predicted from the phase diagram of diblock copolymers. The process according to the invention provides therefore a controllable route to the preparation of new and improved structured materials. Combining inorganic constituents in a hybrid material with organic block copolymers in the nanometer size range gives products with interesting mechanical properties. Since the chemistry of the block copolymers (e.g. their composition, chain length, structure, etc.) can be modified in a know manner it is possible to prepare composites with specific predetermined properties in the manner which has been known for many years for polymers.
Using block copolymers it is further possible to obtain microstructures whose order of size is within the characteristic range of lengths of the polymer chains, i.e. within a size range of from 5 to 100 nanometers. The range of lengths of the structured hybrid materials may be adjusted directly via the molecular weight of the block copolymer used.
The amphiphilic block copolymers used according to the invention as template have at least one hydrophobic and one hydrophilic block. The amphiphilic block copolymers used preferably have A-B, A-B-A or B-A-B structure, particularly preferably A-B structure, where A is a hydrophobic block and B is a hydrophilic block. Each of the individual blocks comprises xe2x89xa65 monomer units, preferably xe2x89xa610 monomer units.
Block copolymers frequently have a further structural unit linking the different blocks to one another. Other amphiphilic polymers preferably used for forming the mesophase therefore have the structure An-Cm-Bn,An-Cm-Bn-Cm-An or Bn-Cm-An-Cm-Bn, where A is a hydrophohic structural unit, B is a hydrophilic structural unit and C is a low- or high-molecular-weight, hydrophobic or hydrophilic structural unit, and n, independently each time it occurs, is an integer xe2x89xa75 and m, independently each time it occurs, is an integer from 0 to 20. C is frequently a coupling molecule or a coupling group linking the individual blocks to one another. A coupling molecule of this type may be used to form a block copolymer by linking a hydrophilic polymer block to a hydrophobic polymer block. It is also possible to begin by polymerizing one of the two blocks, e.g. the hydrophobic block, and then to attach to this block a coupling molecule or a coupling group in order to modify the reactivity of the polymerized block with respect to the monomers, for example by changing the basicity, and then to continue the polymerization with another monomer, e.g. with a hydrophilic monomer.
The individual blocks of the block copolymers used according to the invention are preferably homopolymers, but may also have been prepared from monomer mixtures. At least one, and preferably all, of the hydrophobic blocks of the amphiphilic block copolymer here is/are selected so as to have a glass transition temperature Tgxe2x89xa650xc2x0 C.
Besides diblock copolymers (i.e. block copolymers which essentially comprise two different monomers) it is also possible to use triblock copolymers (i.e. block copolymers essentially comprising three different monomers) or higher block copolymers (i.e. those having more than three different monomers). The use of triblock copolymers as described, for example, by R. Stadler, Macromolecules 28 (1995), 3080-3097 and U. Breiner et al., Makromol. Chem. Phys. 198 (1997), 1051-1083, allows other interesting structures to be obtained which can be derived from the phase diagrams of these triblock copolymers or higher block copolymers.
The hydrophobic fraction of the block copolymer is preferably selected to have a glass transition temperature Tg below the reaction temperature. In this way the equilibrium morphology develops during the reaction of the precursor in the mesophase or, respectively, anisotropic liquid phase of the amphiphilic block copolymer, so that the desired structure based on the equilibrium phase diagram for the block copolymer can be obtained. A hydrophobic block in the amphilphilic block copolymer preferably has a glass transition temperaturexe2x89xa6room temperature, i.e. 25xc2x0 C., particularly preferably xe2x89xa60xc2x0 C. and most preferably xe2x89xa6xe2x88x9225xc2x0 C.
Examples of preferred hydrophobic polymers which may be used as a hydrophobic block in the amphiphilic block copolymer are polyisoprene, polybutadiene, polydimethylsiloxane, methylphenylsiloxane, polyacrylates of C1-C4 alcohols, polymethacrylates of C3-C4 alcohols, and hydrogenated polyisoprene or/and polybutadiene as long as these hydrogenated polymers are not in crystalline form. Particular preference is given to using polyisoprene used as hydrophobic block. Polyisoprene has a glass transition temperature Tg of about 213 K. A high cis-1,4 content in the hydrophobic block, e.g. as present in a polyisoprene block, gives the styrene high mobility at room temperature and allows rapid formation of structures having a long-range order. However, it is also possible to use a interpolymer made from the abovementioned monomers for the hydrophobic block.
The hydrophilic block selected is a polymer miscible with the inorganic precursor in a very wide variety of mixing ratios. Examples of hydrophilic blocks which may be used are polyethylene oxide, polyvinyl alcohols, polyvinylamines, polyvinylpyridines, polyacrylic acid, polymethacrylic acid, hydrophilic polyacrylates and -amides, hydrophilic polymethacrylates and -amides, and also polystyrenesulfonic acids. The hydrophilic fraction of the amphiphilic block copolymer is preferably composed of polyethylene oxide, which is miscible in any desired ratio with most of the known inorganic precursors.
The block copolymer is preferably mixed with the inorganic precursor at xe2x89xa750xc2x0 C., particularly preferably at from 50 to 70xc2x0 C. and most preferably at about 50xc2x0 C. However, the mixing may also take place at lower temperatures, e.g. at room temperature. This results in swelling of the hydrophilic block, e.g. the polyethylene oxide block, by the inorganic precursors.
Preference is given to the use of amphiphilic block copolymers whose molecular weight is from 1000 to 1,000,000 dalton. Amphiphilic block copolymers of this type may be prepared by any known prior art polymerization process, e.g. by cationic, free-radical or anionic polymerization. The anionic polymerization of amphiphilic block copolymers is described, for example, by J. Allgaier et al., Macromolecules 30 (1997), 1582 and in DE-A-2,322,079. The molecular weight is selected as a function of the desired size of the nanostructures. It has been found, for example, that using a polyisoprene-polyethylene oxide block copolymer with a molecular weight of 10,000 dalton gives structures whose size is of the order of 20 nanometers, and using a polyisoprene-polyethylene oxide block copolymer with a molecular weight of 34,000 dalton gives nanostructures whose size is of the order of 40 nanometers. Preference is given to the use of a block copolymer whose polydispersity is low. The polydispersity Mw/Mn is preferably from 1.0 to 1.5, particularly preferably from 1.0 to 1.3 and most preferably from 1.0 to 1.1. Using a low-polydispersity block copolymer can give advantageously high uniformity in the size of the nanostructures.
Preference is given to the use of amphiphilic block copolymers which have a weight ratio of hydrophobic to hydrophilic blocks of from 95:5 to 5:95. By means of the weight ratio of the individual blocks can affect the structure of the mesophase of the block copolymer and the structure of the hybrid material can be affected.
The precursors used may be any desired substances which can be reacted to give an inorganic solid. The term xe2x80x9cinorganic solidxe2x80x9d comprises both ceramic and glassy structures, and also metals. The precursor is preferably an inorganic monomer which reacts to give a solid, e.g. a ceramic, a glass or a metal. The precursor preferably contains Si, Al and/or Ti. Examples of suitable precursors which can be converted into glasses or ceramics are metal alkoxides, such as Si(OR)4, Al(OR)3 and Ti(OR)4 or mixtures of these, where each R is independently a straight-chain or branched, unsubstituted or substituted C1-C8-alkyl radical. Any substituents present are preferably inert, i.e. do not participate in the reaction of the precursors under the prevailing reaction conditions. Examples of substituents of this type are halogen, OH, epoxide, etc. Preferred precursors are silicon alkoxides and aluminum alkoxides. Other preferred precursors used are functionalized orthosilicates of Si(OR3)Rxe2x80x2 type. An Sixe2x80x94C bond is more resistant to hydrolysis than an Sixe2x80x94O bond, and in this way it is therefore possible to introduce functionalized groups into the resultant inorganic structure. The radical Rxe2x80x2 may, for example, comprise a dye, a binding group, a detectable group or the like. This gives a way of providing the inorganic fraction of the material with functional groups in a predetermined and controlled manner. Particular preference is given to the use of precursors containing Si, giving organically modified silicon oxide mesostructures.
Examples of metal-forming precursors are metal compounds which in the presence of the template can form a metallic structure. This metallic structure may, for example, be formed by a chemical reaction, such as a reduction. Preferred metal compounds are metal salts and/or metal complexes, e.g. of noble metals, such as Ru, Rh, Pd, Ag, Os, Ir, Pt, Au or mixtures of these. The reaction of the precursor to give the solid may take place in various ways by reactions known from the prior art. For example, the solid may be formed by condensation of metal alkoxides in the mesophase, by oxidic or sulfidic precipitation on the template, or by reduction of metal salts on the template.
The composition and structure of the organic inorganic hybrid materials may be determined via the weight ratio of block copolymer to inorganic precursor. The weight ratio of block copolymer to precursor is preferably from 5:95 to 95:5. The structure of the organic-inorganic hybrid material depends on the ratio between the amount of the block copolymer and the amount of the inorganic precursor which becomes concentrated in the hydrophilic block of the block copolymer. The respective structure can be found from equilibrium phase diagrams for the compounds selected. Preference is giving to using an excess of the block copolymer, i.e. a ratio of from 50:50 to 95:5 between this and the precursor. This gives an organic-inorganic hybrid material with a matrix made from organic polymer, into which inorganic formed pieces of an order of size within the nanometer range have been embedded with a predetermined structure.
The solvent is particularly preferably removed from the reaction mixture prior to reacting the precursor to give the solid. The solvent used here may be water or an organic solvent. The solvent used is preferably one in which both the hydrophilic and the hydrophobic blocks of the block copolymer are soluble, for example a chlorinated hydrocarbon or a linear or cyclic ether, in particular chloroform, tetrahydrofuran or mixtures of these. It is also preferable for the inorganic precursor also to have at least some solubility in the solvent used. In this particularly preferred method of conducting the process the solvent serves merely for mixing of the individual components. After the components have been mixed together, in particular the organic block copolymer and the precursor, the solvent is removed from the reaction mixture, for example by evaporation or by vaporization if desired in vacuo. The reaction of the inorganic precursor to give the solid then takes place in a bulk phase or, respectively, in a mesophase essentially free from solvents. Surprisingly, it has been found that the structure of the hybrid material according to the invention in this case can be taken directly from the phase diagram for block copolymers. For example, if a PI-b-PEO block copolymer is used the resultant structure is predetermined directly from the phase diagram for this diblock copolymer. This is attributable to the fact that, unlike the procedure of the prior art (C. G. Gxc3x6ltner et al., Adv. Mater. 9 (5), (1997), 431-436) the template used is not a lyotropic liquid-crystal phase of a block copolymer but rather a bulk phase or, respectively, mesophase formed by the block copolymer itself. The structure does not therefore depend on the concentration of the block copolymer in solution or on the nature of the solvent needed to form the lyotropic liquid-crystal phase, but is determined directly by the composition of the block copolymer, i.e. by the ratio of the hydrophobic to hydrophilic blocks (including any incorporated inorganic constituents). In this way it is possible to determine the desired innovative structures of the hybrid material of the invention directly from the phase diagram for the block copolymers by selecting appropriate starting compounds. In this method of conducting the process it is preferable for the solvent to be removed from the reaction mixture to an extent of more than 50%, particularly preferably more than 90%, most preferably more than 99%, i.e. quantitatively, prior to reacting the precursor.
According to the invention it is also possible to carry out the entire process without solvent. In this case both the inorganic precursor, in particular a sol of the inorganic precursor, and the hydrophobic part of the block copolymer, in particular a block with a glass transition temperature below the mixing temperature, serve to promote thorough mixing of the components. There is then no need for removal of solvent prior to the reaction. This embodiment preferably uses a hydrophilic block with a low glass transition temperature, preferably Tgxe2x89xa650xc2x0 C., particularly preferably Tgxe2x89xa625xc2x0 C. and most preferably Tgxe2x89xa60xc2x0 C. This hydrophilic block is not crystalline at the mixing temperature, and the inorganic precursor and the block copolymer can therefore be mixed directly without the intervention of a solvent.
The organic-inorganic hybrid material is preferably obtained as an anisotropic formed piece. If the organic-inorganic hybrid material is obtained in the form of particles with dimensions in the micrometer range, within the particles there are structures with local anisotropic orientation and an order of size within the nanometer range. When formed pieces are compression-molded from powders of this type, however, the result is a macroscopically isotropic solid, since the locally anisotropic grains have random orientation. However, it is frequently desirable to obtain materials with macroscopically anisotropic orientation. In this case the organic-inorganic hybrid material is obtained as an anisotropic formed piece, e.g. in the form of a monolith, as a film or as a block. This is preferably done by using the process known as solvent casting, in which the reaction mixture is cast into thin layers (thickness from about 1 to 10 mm) and then reacted. Removal of the solvent gives quasi-single crystals which have macroscopic orientation due to the interactions of the block copolymers with the substrate. By repeating this procedure a number of times it is possible to build up thicker structures.
According to the invention it is also possible to remove the template after forming the organic-inorganic hybrid material. This is preferably done by calcination and/or extraction. In this case on the one hand it is possible to obtain mesoporous materials which have high particle diameters and can be used, for example, in catalyst technology. On the other hand, if the ratio of the starting materials is selected suitably, removing the template can remove the organic matrix which surrounds the embedded inorganic formed pieces in the nanometer size range. This gives solid inorganic formed pieces with a size in the nanometer range.
The process of the invention may be carried out using the sol-gel process. Here, a first step uses water to hydrolyze an organic precursor having alkoxy groups, e.g. Si(OCH3)4, forming a sol comprising Si(OH)4. A second step of the reaction then condenses the sol, forming a gel containing Sixe2x80x94Oxe2x80x94Si bonds. This sol-gel process may be carried out in an aqueous solvent, and the first step of the reaction then takes place in an aqueous mixture comprising the block copolymer as template and comprising the organic precursor. However, for many applications it is advantageous for the organic-inorganic hybrid material to be obtained free from water. The invention therefore also includes a process for preparing structured organic-inorganic hybrid materials, comprising the steps:
(a) preparing a sol comprising a precursor which can be reacted to give an inorganic solid,
(b) adding the sol from (a) to a mesophase of an amphiphilic block copolymer as template,
(c) reacting the precursor and forming a gel,
(d) optionally removing any volatile constituents from the reaction mixture, and
(e) obtaining the organic-inorganic hybrid material.
Preferred features of this process are as described above.
The sol is preferably formed by at least partial hydrolysis of a precursor which can react to give an inorganic solid. Precise metering of the starting materials here can avoid the presence of excess water in the sol. This method of conducting the process preferably uses an organic solvent in which both the hydrophilic and the hydrophobic blocks of the block copolymer are soluble, preferably a chlorinated hydrocarbon or a linear or cyclic ether, particularly preferably chloroform, tetrahydrofuran or mixtures of these. By carrying out the process in this way the block copolymer does not have to be brought into contact with water, and water-free hybrid materials can therefore be obtained. Here again, the solvent is preferably removed from the mixture prior to reacting the precursor, giving the advantages discussed above.
Surprisingly, it has been found that adding salt to the reaction mixture can prevent any type of macroscopic phase separation from occurring between organic and inorganic phases. The reaction mixture therefore preferably also comprises a salt, thereby ensuring that the process can be carried out successfully and reproducibly. The salt here may be added to the block copolymer straightaway prior to forming the mesophase, for example straightaway during the anionic polymerization of the block copolymer. However, it is also possible for the salt to be added directly to the reaction mixture. The amount of the salt added here is from 0.01 to 5% by weight, preferably from 0.1 to 1% by weight, based on the total weight of the block copolymer used. If an organic solvent is used, THF for example, the reaction is preferably carried out in a salt-saturated solution. The salt is particularly preferably selected from the group consisting of salts known as network modifiers in glasses. Network modifiers of this type give rise to structural defects in amorphous inorganic glasses. It is likely that the hydrophilic part of the copolymer, which is swelled by the inorganic material, can become anchored into the structural defects formed by the salt in the inorganic lattice, preventing phase separation. The salts used preferably contain mono- or bivalent cations, such as alkali metal, alkaline earth metal and/or transition metal cations. The counterions used may be inorganic or organic anions, preferably inorganic ions and particularly preferably halide ions. Suitable salts are NaCl, KCl, CaCl2 and the like.
The salt, used particularly preferably comprises potassium chloride.
Surprisingly, it has been found that the presence of salt is a factor which makes it substantially easier to carry out the process successfully. The present invention therefore also includes a process for preparing structured organic-inorganic hybrid materials, comprising the steps:
(a) forming a mixture comprising at least one mesophase of an amphiphilic organic block copolymer as template and comprising at least one precursor which can be reacted to give an inorganic solid,
(b) reacting the precursor,
(c) optionally removing any volatile constituents from the reaction mixture, and
(d) obtaining the organic-inorganic hybrid material, wherein the mixture formed in step (a) also comprises a salt.
This process is preferably carried out using the starting materials and further steps given above. The use of a salt can almost completely prevent phase separation of organic and inorganic phase in the reaction mixture, making it possible to prepare reproducible organic-inorganic hybrid materials with structures in the nanometer size range.
The invention also provides an organic-inorganic hybrid material obtainable by the processes described above. A hybrid material of this type features in particular regular structures of from 5 to 100 nanometers, preferably from 20 to 100 nanometers in size. The structures are preferably nanocylinders or nanolamellae, and the hybrid material here has a periodicity of xe2x89xa75 nanometers. Depending on the selection of the starting materials and of their proportions, and on the selection of the process conditions, the resultant hybrid material may on the one hand comprise an essentially organic matrix into which inorganic structures have been embedded or on the other hand be a hybrid material which comprises an essentially inorganic matrix into which the organic block copolymer used as template has been embedded. A hybrid material of this type is preferably in the form of an anisotropic solid, for example a monolith with edge length of from 0.1 mm to 10 cm, preferably from 1 mm to 1 cm, or a film.
If the hybrid material comprises an inorganic matrix with organic structures embedded therein, partial of complete removal of the template from the hybrid material of the invention gives a mesoporous solid which is likewise provided by the invention. A solid of this type preferably has a pore diameter of from 5 to 100 nanometers, particularly preferably from 20 to 100 nanometers. By suitably selecting the block copolymer, in particular by using a block copolymer with a low polydispersity, it is possible to obtain a mesoporous solid with uniform pore diameters. If the hybrid material comprises an organic matrix with inorganic structures embedded therein it can serve as starting material for producing formed pieces consisting of organic-inorganic hybrid material or of inorganic material and preferably having a diameter of from 5 to 100 nanometers. Formed pieces of this type are obtained by using organic solvents, such as tetrahydrofuran, to dissolve an organic-inorganic hybrid material with an organic matrix. After dissolving the material, residual organic constituents may be removed completely or partially by calcination. Formed pieces of this type are preferably in the form of spheres, cylinders or lamellae. By using triblock copolymers access can be gained to other new structures, such as spirals. The structures desired here are taken from the phase diagrams for triblock copolymers, and the structuring block is hydrophilic. Phase diagrams for triblock copolymers are described, for example, by R. Stadler et al., Macromolecules 28 (1995), 3080-3097 and U. Breiner et al., Makromol. Chem. Phys. 198 (1997), 1051-1083. Formed pieces with interesting new structures can be produced in this way.
After organic solvents have been used to dissolve the materials the hydrophilic polymer blocks remain in the inorganic phase. Hydrophobic polymer blocks can then protrude out of the inorganic phase, giving xe2x80x9chairyxe2x80x9d solids or, respectively, formed pieces.
After removal of the organic constituents by calcination, the walls of the burnt materials are themselves, nanoporous beyond the expected pores, in particular if a polymer having hydrophilic polyethylene oxide blocks is used, which can be embedded to some extent or completely into the ceramic phase. The sintering process moreover gives relatively large cavities in the range from 50 to 200 nm, e.g. about 100 nm. The occurrence of these relatively large cavities is a very desirable phenomenon since it increases the flow rate and thus the output rate in physical separation processes.
The process of burning the organic material out of the organic-inorganic hybrid materials preferably takes place in stages which may include microscopically continuous shrinkage. In the case of mesoporous solids with an inorganic matrix the average distance between two pores decreases to about 60-70% of the initial value, while the pore diameter decreases to about 75-85% of the initial value. Measurements of pore volume using BET nitrogen adsorption showed that internal surface areas of 300 m2/g, for example, could be obtained. Oxygen calcination gives a bimodal pore size distribution, e.g. pore diameters of about 10 nm and 4 nm, both pores occurring with comparable frequency (in each case at least 30% of the pore total). In contrast, air calcination can virtually prevent any production of the smaller type of pore.
The materials prepared according to the invention are preferably used in separation technology, in particular in the form of films. However, they are also highly suitable as solids for use in heterogeneous catalysis and in macroelectronics.